Cyclonic separating apparatus with tangential offtake conduit

ABSTRACT

The invention provides cyclonic separating apparatus comprising a tapering cyclone having a larger end a smaller end, a fluid outlet located at the larger end of the cyclone, the fluid outlet becoming located coaxially with the cyclone, and a tangential offtake conduit communicating with the fluid outlet, wherein the distance between the tangential offtake conduit and the smaller end of the cyclone increases in the downstream direction of the tangential offtake conduit. Preferably, the tengential offtake conduit follows a substantially helical path. This reduces the turbulence created in the tangential offtake conduit and allows kinetic energy of the exiting fluid to be recovered as pressure energy.

TECHNICAL FIELD OF THE INVENTION

The invention relates to cyclonic separating apparatus. Particularly,but not exclusively, the invention relates to cyclonic separatingapparatus for use in vacuum cleaners.

BACKGROUND OF THE INVENTION

Cyclonic separating apparatus in which particulate material is separatedfrom a fluid, usually a gas, by means of high centrifugal forces isknown. Such apparatus comprises a tapering cyclone body having a fluidinlet located at the larger end of the cyclone body and arranged tointroduce fluid to the interior surface of the cyclone body in atangential manner. The smaller end of the cyclone body is surrounded bya collector or, alternatively, leads to a particulate material outlet. Afluid outlet in the form of a vortex finder is located centrally of thelarger end of the cyclone body. In use, the fluid inlet introduces thefluid with the particulate material entrained therein to the interior ofthe cyclone body in a tangential manner. The taper of the cyclone bodycauses the fluid to be accelerated down the length of the cyclone bodywhich causes the particulate matter to be separated from the fluid andto collect in the collector or, if appropriate, to exit the apparatusvia the material outlet. The fluid forms a vortex generally along thelongitudinal axis of the cyclone body and exits the apparatus via thevortex finder at the centre of the larger end of the cyclone body.

When the exiting fluid passes through the vortex finder, it is spinningwith a high angular velocity. If the offtake conduit leading from thevortex finder is linear with respect to the vortex finder (ie. theconduit has a central axis which is continuous with the central axis ofthe vortex finder), then the outgoing fluid will continue to spin as ittravels along the conduit but will, eventually, revert to linear flowand the kinetic energy of the fluid flow associated with the spinningmovement will be lost, probably in the form of frictional losses. Someattempt has been made to recover some of the kinetic energy of thespinning exiting fluid by utilising tangential offtakes from the vortexfinder. The offtake is positioned so as to be tangential to one side ofthe vortex finder so that the spinning fluid enters the offtake in alinear manner. Examples of tangential offtakes used in conjunction withcyclonic separators are shown and described in the paper entitled “TheUse of Tangential Offtakes for Energy Savings in Process Industries” byT. O'Doherty, M. Biffin and N. Syred (Journal of Process MechanicalEnginering, Vol. 206, Page 99ff). The arrangements shown and describedin this paper attempt to convert some of the kinetic energy of the fluidflow into pressure energy. However, the pressure recovery is not whollysuccessful. This is partly due to the fact that the fluid flow exitingthe cyclonic separator is still required to follow a path which containssharp changes in direction. In the paper referred to above, thetangential offtakes are each located within a horizontal plane whichrequires the axial velocity component of the exiting fluid to be turnedthrough a 90° angle in a short distance. This results in turbulent flowdownstream of the vortex finder which leads to energy loss from thefluid.

One application of such separators is in vacuum cleaners in which dirtand dust particles are separated from an airflow within the vacuumcleaner so that, when dirty air is drawn into the cleaner, the dirt anddust particles are separated from the airflow and retained for disposalwhilst clean air is expelled. Vacuum cleaners of this type are shown anddescribed in various prior published patents, such as EP 0 042 723, EP 0636 338 and EP 0 134 654. Recovery of a higher proportion of the kineticenergy of the fluid exiting the cyclonic separating apparatus wouldresult in a vacuum cleaner having a higher efficiency and thus a betterlevel of performance.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide cyclonic separatingapparatus in which a greater proportion of the kinetic energy of exitingfluid is recoverable. It is a further object of the present invention toprovide cyclonic separating apparatus which, when incorporated into avacuum cleaner, results in the vacuum cleaner performing with a higherefficiency and/or better performance.

The invention provides a cyclonic separating apparatus comprising atapering cyclone having an axis, a larger end and a smaller end, a fluidinlet and a fluid outlet located at the larger end of the cyclone, thefluid outlet being located coaxially with the cyclone, and a tangentialofftake conduit communication with the fluid outlet, wherein thedistance, measured parallel to the axis, between the tangential offtakeand the smaller end of the cyclone increases in the downstream directionof the tangential offtake conduit. Preferably, the tangential offtakeconduit follows a substantially helical path downstream of the fluidoutlet. Such an arrangement allows the fluid exiting the separatingapparatus to be gradually turned through a required angle withoutimposing sharp changes of direction. This reduces the amount ofturbelence induced in the fluid flow by virtue of the direction changeand this in turn reduces energy loss through friction.

The invention provides cyclonic separating apparatus comprising atapering cyclone having an axis, a larger end and a smaller end, a fluidinlet and a fluid outlet located at the larger end of the cyclone, thefluid outlet being located coaxially with the cyclone, and a tangentialofftake conduit communicating with the fluid outlet, wherein thedistance, measured parallel to the axis, between the tangential offtakeand the smaller end of the cyclone increases in the downstream directionof the tangential offtake conduit. Preferably, the tangential offtakeconduit follows a substantially helical path downstream of the fluidoutlet. Such an arrangement allows the fluid exiting the separatingapparatus to be gradually turned through a required angle withoutimposing sharp changes of direction. This reduces the amount ofturbulence induced in the fluid flow by virtue of the direction changeand this in turn reduces energy loss through friction.

The tangential offtake conduit preferably has a central axis which isinclined at an angle of between 35° and 70°, preferably 60°, to thelongitudinal axis of the cyclone body. This arrangement turns theexiting fluid through a required angle without significantly increasingthe possibility of separation occurring as the fluid passes through thetangential offtake conduit. It also allows the kinetic energy of thespinning fluid to be recovered as pressure energy which in turn resultsin the provision of a highly efficient system for separation ofparticles from a fluid.

In a preferred embodiment, a centerbody is located in the fluid outlet,which consists of a vortex finder. The tangential offtake conduit thencommunicates with an annular chamber delimited on the outside by thefluid outlet and on the inside by the centerbody. The arrangement of anannular chamber around the centerbody ensures that all of the exitingair is aligned with the tangential offtake conduit so that the amount ofturbulence introduced at the entrance to the tangential offtake conduitis kept to a minimum.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings, wherein:

FIG. 1 is a side view of a vacuum cleaner incorporating cyclonicseparating apparatus according to the invention;

FIG. 2 is a view of the vacuum cleaner of FIG. 1 taken along arrow A;

FIG. 3 is a partially cut-away view of part of the vacuum cleaner ofFIG. 1, including the cyclonic separating apparatus;

FIG. 4 is a side view of a tangential offtake conduit and centerbodyforming part of cyclonic separating apparatus according to theinvention; and

FIG. 5 is a plan view of the tangential offtake conduit and centerbodyof FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Cyclonic separating apparatus according to the invention can beincorporated to good effect in a vacuum cleaner. A vacuum cleanerincorporating cyclonic separating apparatus according to the inventionis shown in FIGS. 1 and 2. The vacuum cleaner 10 has a chassis 12 whichsupports a motor and fan unit 14 and cyclonic separating apparatus 50.Support wheels 16 are mounted on the chassis 12 towards the rear thereofand a castor wheel 18 is arranged beneath the chassis 12 towards thefront thereof to allow the cleaner 10 to be maneouvred across a surfaceto be cleaned The motor and fan unit 14 is arranged substantiallybetween the support wheels 16 to give the cleaner 10 a high degree ofmaneouvrability.

The cyclonic separating apparatus 50 is designed to effect theseparation of dirt and dust particles from an airflow which is drawninto the cleaner 10 by the motor and fan unit 14. A hose (not shown)carrying a floor tool is connected to an air inlet 20 of the cyclonicseparating apparatus 50 so that the dirty airflow can be drawn into themachine. The dirty air passes into the cyclonic separating apparatus 50which operates in a known manner to extract, initially, larger dirt andfluff and, subsequently, finer dirt and dust particles from the airflow.The airflow from which dirt and dust has been extracted passes out ofthe cyclonic separating apparatus 50 and then to the motor and fan unit14 via an offtake conduit 22. The airflow passes through the fan andaround the motor so as to provide a cooling effect in a known manner.Pre- and post-motor filters (not shown) can be provided in housings 24,26 in order to protect the motor and to prevent particulates releasedfrom the motor brushes from being released into the atmosphere. Theclean air is exhausted to atmosphere via a clean air outlet 28.

A cover portion 30 is hingedly attached to the chassis 12 about a hinge32 to provide access to the pre-motor filter housing 24 so that thepre-motor filter can be replaced periodically. The cover portion 30 alsoreleases the cyclonic separating apparatus to allow it to be removedfrom the chassis 12 for emptying purposes as and when necessary. Thecover portion 30 includes the offtake conduit 22 and a carrying handle34.

Having described the basic structure and operation of the vacuum cleaner10, the cyclonic separating apparatus 50 will now be described in moredetail with reference to FIG. 3. It will be appreciated that theseparating apparatus itself, ie the cyclone arrangement, is known anddetails can be found in, inter alia, EP 0134 654B. Essentially, thecyclonic separation apparatus 50 comprises an outer cyclone 52 and aninner cyclone 54. The outer cyclone comprises a generally cylindricalcontainer or bin 56 having a side wall 56 a, a base 56 b and atangential inlet 58. The inner cyclone 54 comprises a frusto-conicalcyclone body 60 depending from an upper surface 62 of the separatingapparatus 50 The inner cyclone 54 has a cone opening 64 at the lower endthereof and a tangential inlet 66. Depending between the side wall 56 aof the outer cyclone 52 and the inner cyclone body 60 is a shroud 68which is substantially cylindrical in shape and includes a multiplicityof perforations 70 within a cylindrical band 68 a of the shroud 68. Theshroud 68 is supported by way of a flange 68 a extending between theshroud 68 and an upper portion of the outer cyclone 52. The shroud 68 isalso sealed to the outer surface of the cyclone body 60 at the lower endof the shroud 68. The upper part of the interior of the shroud 68communicates with the tangential inlet 66. Below the shroud 68, a finedust collector 72 is positioned so that it surrounds the cone opening64. The fine dust collector 72 is sealed to the base 56 b of thecontainer 56 and also to the cyclone body 60 so that a closed collectoris formed around the cone opening 64. A cylindrical vortex finder 74 ispositioned centrally of the upper surface 62 so that it extends into theinterior of the inner cyclone 54 along the axis of the frusto-conicalcyclone body 60.

In use, as will be understood from the prior art, dirty air enters thecyclonic separating apparatus 50 via the tangential inlet 58. Thetangential nature of the inlet 58 forces the incoming air to follow aspiral path in a swirling motion around the interior surface of thecontainer 56 so that larger dirt and fluff particles become separatedfrom the airflow and collect in the lower area of the container 56 ontop of the fine dust collector 72. The airflow moves inwardly towardsthe upper portion of the fine dust collector 72 and then travels, stillswirling, up the outer surface of the shroud 68. The airflow thentravels through the perforations 70 in the shroud 68 and is thenintroduced to the interior of the inner cyclone 54 via the tangentialinlet 66. The tangential nature of this inlet 66 also forces the airflowto follow another spiral path inside the cyclone body 60. Thefrusto-conical shape of the cyclone body 60 causes the velocity of theairflow to increase as it travels down the cyclone body 60 and the highspeeds attained by the airflow allow very small particulates of dirt anddust to be separated from the airflow and collected in the fine dustcollector 72. The clean airflow then forms a vortex substantially alongthe longitudinal axis of the cycone body 60 which exits the innercyclone 54 by way of the vortex finder 74.

As has been stated, the construction and operation of such separationapparatus is well known and the finer details need not be described anyfurther. The invention lies in the vortex finder 74 and the offtakeconduit 22 located immediately downstream of the vortex finder 74. Theinvention is therefore applicable to any cyclonic separating apparatushaving a frusto-conical cyclone body in which a vortex is created and inwhich the exiting air is carried out of the apparatus via a vortexfinder.

As can be seen from FIG. 3, the vortex finder 74 is cylindrical anddepends from the upper surface 62 into the inner cyclone 54 by means ofan inclined support wall 62 a. The vortex finder 74 also extendsupwardly from the support wall 62 a so that the vortex finder 74terminates in a plane level with the upper surface 62, although this isnot critical. Extending along the central axis of the vortex finder 74is a centerbody 76 which is generally cylindrical but may taper slightlyfrom the upper end towards the lower end. The centerbody 74 has ahemispherical distal end 76 a which terminates within the vortex finder74 without extending beyond the lower end thereof. Again, this is notcritical. The vortex finder 74 communicates with a chamber 78 locatedimmediately above the vortex finder 74 and at the upstream end of thetangential offtake conduit 22. The chamber has an arcuate outer wall 80which has a generally spiral shape so that the chamber 78 communicateswith the tangential offtake 22 in the manner of a scroll.

The centerbody 76 is formed integrally with a support portion 84 whichis shaped so as to fit inside the upper end of the chamber 78 and toabut against the roof of the chamber 78. The support portion 84 definesthe upper boundary of the chamber 78 and also provides support for thecenterbody 76. The shape of the lower surface 86 of the support portion84 is generally helical to form a scroll with a roughly constantcross-sectional area and is contiguous with the tangential offtakeconduit 22. The tangential offtake conduit 22 communicates with thechamber 78 in a scroll-like manner and then follows a path whichincreases in distance from the cone opening 64 in the direction of theairflow. The tangential offtake conduit 22 is also slightly arcuate inplan view as can be seen from FIG. 2. After a predetermined distance,the portion of the tangential offtake conduit 22 ceases to increase indistance from the cone opening 64 and is then directed towards thehousing 24 of the pre-motor filter. The tangential offtake conduit 22,opens into the housing 24 at an inlet 88.

A helical offtake conduit 122 suitable for use in the vacuum cleaner 10of FIGS. 1 and 2 is shown in isolation in FIGS. 4 and 5. Also shown arethe chamber 178 and the centerbody 176 which form part of the sameconstructional piece. The centerbody 176 projects along an axis 200which is, in use, coaxial with the axis of the vortex finder 74 shown inFIG. 3. A cylindrical neck 190 surrounds the centerbody 176 and carriesa seal 192 which, in use, abuts against the upper lip of the vortexfinder 74 to form a seal therewith. The neck 190 opens into the chamber178 which, as can be seen from FIG. 5, is spiral in shape so as to allowthe tangential offtake conduit 122 to communicate with the chamber 178in a scroll-manner. The tangential offtake conduit 122 then leaves thechamber 178 at an acute angle with respect to the axis 200 of thecenterbody. The tangential offtake conduit 122 has a central axis 202which meets the axis 200 at an angle a which is ideally about 60° butcan vary between 35° and 70°. The distance (measured parallel to theaxis 200) between the tangential offtake conduit 122 and thehemispherical end 176 a of the centerbody 176 increases with distancealong the tangential offtake conduit 122. The arcuate shape of thetangential offtake conduit 122 can be seen clearly in FIG. 5. The distalend 122 a of the conduit 122 is shaped and arranged to communicatedirectly with the pre-motor filter housing 24 (see FIG. 1). A seal canbe arranged around the open mouth of the distal end 122 a of the conduit122 if desired.

When fluid leaves the cyclonic separating apparatus 50 shown in FIG. 3via the vortex finder 74, it is spinning with a high angular velocity.The angular velocity is still very high as the fluid flow enters thechamber 78. However, the scroll-like connection between the tangentialofftake conduit 22 and the chamber 78 allows the spinning fluid to enterthe offtake conduit 22 in a tangential manner and to progress along theofftake conduit 22 as a linear flow. The helical shape of the lowersurface 86 of the support portion 84 guides the spinning fluid into theopen end of the tangential offtake conduit 22. Furthermore, because thetangential offtake conduit 22 is inclined to the axis of the vortexfinder 74 and thereby increases in its distance from the cone opening 64in the downstream direction, the fluid flow is not turned through asharp 90° bend which means that less turbulence than would otherwise bethe case is induced in the flow. The helical formation of the offtakeconduit 22 provides a smooth path for the fluid exiting the separatingapparatus so that as much as possible of the kinetic energy of thespinning fluid is recovered as pressure energy. This energy recoveryresults in a higher efficiency of the apparatus overall.

It will be appreciated that a helical or inclined tangential offtake canbe applied to any situation where separation takes place in a cyclonewith a vortex finder providing the outlet for the fluid. The applicationto a vacuum cleaner is described above but the invention is not to beregarded as limited to such an application. Other applications areenvisaged such as other types of separation or filtration system forseparating particulates from a fluid, eg. diesel exhaust systems and airconditioning systems.

What is claimed is:
 1. Cyclonic separating apparatus comprising atapering cyclone having an axis, a larger end and a smaller end, a fluidinlet and a fluid outlet located at the larger end of the cyclone, thefluid outlet being located coaxially with the cyclone, and a tangentialofftake conduit communicating with the fluid outlet, wherein thedistance, measured parallel to the axis, between the tangential offtakeconduit and the smaller end of the cyclone increases in the downstreamdirection of the tangential offtake conduit and the tangential offtakeconduit follows a helical path downstream of the fluid outlet. 2.Cyclonic separating apparatus as claimed in claim 1, wherein thetangenital offtake conduit is inclined at an angle of between 35° and70° to the longitudinal axis of the cyclone body.
 3. Cyclonic separatingapparatus as claimed in claim 2, wherein the tangential offtake conduithas a central axis which is inclined at an angle of between 50° and 65°to the longitudinal axis of the cyclone body.
 4. Cyclonic separatingapparatus as claimed in claim 3, wherein the central axis is inclined atan angle of substantially 60° to the longitudinal axis of the cyclonebody.
 5. Cyclonic separating apparatus as claimed in claim 1, whereinthe fluid outlet consists of a vortex finder.
 6. Cyclonic separatingapparatus as claimed in claim 1, wherein a centerbody is located in thefluid outlet.
 7. Cyclonic separating apparatus as claimed in claim 6,wherein the tangential offtake conduit communicates with an annularchamber delimited on the outside by the fluid outlet and on the insideby the centerbody.
 8. A vacuum cleaner incorporating a cyclonicseparating apparatus comprising a tapering cyclone having an axis, alarger end and a smaller end, a fluid inlet and a fluid outlet locatedat the larger end of the cyclone, the fluid outlet being locatedcoaxially with the cyclone, and a tangential offtake conduitcommunicating with the fluid outlet, wherein the distance, measuredparallel to the axis, between the tangential offtake conduit and thesmaller end of the cyclone increases in the downstream direction of thetangential offtake conduit.
 9. The vacuum cleaner according to claim 8,wherein the cyclonic separating apparatus is adapted to separate dirtand dust particles from air flow.
 10. The vacuum cleaner according toclaim 8, wherein the tangential offtake conduit communicates with apre-motor filter located immediately upstream of a motor and fan unit.11. The vacuum cleaner according to claim 8, wherein the tangentialofftake conduit follows a helical path downstream of the fluid outlet.12. The vacuum cleaner according to claim 11, wherein the tangentialofftake conduit is inclined at an angle of between 35° and 70° to theaxis of the cyclone body.
 13. The vacuum cleaner according to claim 11,wherein the tangential offtake conduit has a central axis inclined at anangle of between 50° and 65° to the axis of the cyclone body.
 14. Thevacuum cleaner according to claim 11, wherein the tangential offtakeconduit is inclined at an angle of about 60° to the axis of the cyclonebody.
 15. The vacuum cleaner according to claim 11, wherein the fluidoutlet includes a vortex finder.
 16. The vacuum cleaner according toclaim 11, wherein a centerbody is located in the fluid outlet.
 17. Thevacuum cleaner according to claim 16, wherein the tangential offtakeconduit communicates with an annular chamber delimited on the outside bythe fluid outlet and on the inside by the centerbody.